High frequency amplifier and frequency multiplier



June 15, 1937. R. H. VAN MINNEIN ET AL 2,083,755

HIGH FREQUENCY AMPLIFIER AND FREQUENCY MULTIPLIER Filed May 15, 1954 Patented June 15, 1937 UNITED STATES PATENT OFFICE HIGH FREQUENCY AMPLIFIER AND FRE- QUENCY MULTIPLIER Application May 15, 1934, Serial No. 725,800. In Germany May 16, 1933 3 Claims.

In our United States application #702,852 filed December 18, 1933 now United States Patent #2,034,848 issued March 24, 1936, a circuit arrangement for high frequency amplifiers and frequency multiplication arrangements has been described in which the reaction of the output circuit on the input circuit caused by the inter electrode capacity of the amplifying tube is balanced by the capacity between Cathode and one or more of the electrodes thereof or of another tube, instead of by separate neutralizing condensers, as was customary in the circuit arrangements hitherto used.

In said patent specification it has been set out that in order to ensure proper working of the push-pull arrangements disclosed, it is absolutely necessary that the cathodes of the tubes acquire a high frequency potential.

In the arrangements referred to this object is accomplished by inserting choking coils in the feeders of the filaments.

One of the primary objects of this application is to provide an arrangement of the type disclosed in said United States Patent #2934348 by means of which the cathodes of two pushpull connected tubes can maintain or acquire a high frequency potential, without the use of separate choking coils interposed in the feeders of the filaments.

This invention will be more clearly understood by reference to the attached drawing representing, by way of example, one form of construction thereof.

In this drawing the input circuit consists of a variable condenser I l and of two induction coils L connected in parallel. Both ends of these coils L are connected together through two condensers C1, C2 as shown. The condensers C1, C2 are of small impedance to high frequency currents and are as shown connected to the ends of the filaments f1 and f2 of tubes a1 and a2. In this case the heating current for the tubes is supplied from any source to the middle of both induction coils by leads l2 and I2. In this manner the filaments of the tubes can acquire a high frequency potential. The filaments may be heated by direct current or by alternating current as shown.

The anodes of the tubes are connected together by means of a tuned circuit II], II Which may be tuned to the frequency of the wave to be amplified or a harmonic thereof. Potential for the anode electrodes is supplied from a source of direct current connected as shown between a point on the inductance l0 and ground. The

source is shunted by a bypass condenser. Each control grid is connected to ground by Way of a choking inductance and a biasing resistance.

The high frequency potentials to be amplified or multiplied are supplied from any source to the leads connected with the condenser l4 and from said leads to the terminals of the inductances L between the filaments. The condenser M tunes this circuit to the frequency of the applied oscillations. The condensers c1 and c2 short-circuit the inductances L at their terminals for the radio frequency potentials supplied, so that said potentials Will be applied to both sides of both filaments in like phase, the phases at each end of the inductances being unlike.

As in the prior United States application referred to above, neutralizing is accomplished by connecting the control grids g1, Q2 of each tube to the electrical center of a condenser system connected in shunt to the filament of the other tube, as shown. Thus, if we consider a single tube the grid to anode capacity is compensated by the anode to filament capacity if they are equal. If we consider a bridge circuit formed by the two tubes the anode to grid capacity of tube on is balanced against the anode to grid capacity of tube a2 and the anode to filament capacity of a1 balances the anode to filament capacity of (12. These neutralization circuits are obvious and need no further description here although they have been described and illustrated more in detail in said Patent #2,034,898. Thus, voltage difierences across I0, ll cannot affect C1, L, C2, and vice versa, provided the anode to filament capacities of the tubes are equal to the anode to grid capacities of the tubes.

Having thus described our invention and the operation thereof, what we claim is:

1. In a high frequency amplifier, a pair of thermionic tubes each having an anode, a filament, and a control grid, a tuned impedance connected between the anodes of said tubes, a self-biasing circuit connected between the grid and cathode of each tube, a connection between the filament of each tube and the grid of theother tube, parallel reactances connecting the terminals of the filament of one of said tubes to the terminals of the filament of the other of said tubes, a circuit connected to said reactances for applying heating potentials for said filaments to the electrical centers of said parallel reactances, and a circuit connected to said reactances for applying oscillations to be amplified to the terminals of said parallel reactances.

2. A high frequency repeating device comprising a pair of thermionic tubes each having an output electrode, a control electrode and a filamentary emission element, an output circuit connected to said output electrodes, a condenser connected between the terminals of each filamentary emission element, an inductance connecting one end of the filament of one tube to one end of the filament of another tube, a similar inductance connecting the other end of the filament of said one tube to the other end of the filament of said other tube, said inductances being short-circuited at their terminals by said condensers for high frequency potentials, means for tuning said inductances to the frequency of the oscillations to be repeated, an input circuit connected to said inductances, and a filament heating circuit connected to said inductances.

3.,In a high frequency relay, a pair of thermionic relay tubes each having an anode, a filamentary cathode, and a control grid, a tuned impedance connected between the anodes of said tubes, a self-biasing circuit connected between the grid and cathode of each tube, a connection between the grid of each tube and the filamentary cathode of the other tube, an inductance connecting one terminal of the filamentary cathode of one of said tubes to one terminal of the filamentary cathode of the other of said tubes, an inductance connecting the other terminal of the filamentary cathode of said one of said tubes to the other terminal of said filamentary cathode of said other of said tubes, radio frequency bypass condensers connected between the terminals of said inductances to short-circuit said terminals for radio frequency potentials, means for applying cathode heating current to the electrical centers of said inductances, and means for applying radio frequency potentials to be relayed to said inductances.

RINFE HENDRIK VAN MINNEN. PIERRE JANNE HENRI ALPHONSE NORDLOHNE. 

